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emUSB-Device CDC

  • Check and set Line Coding and Line States
  • No host driver required for Windows / Linux / macOS
  • Small footprint



About the Communications Device Class

The USB Communications Device Class (CDC) allows to convert the USB device into a serial communication device. It is an abstract USB class protocol defined by the USB Implementers Forum. This protocol allows devices to provide a virtual COM port to a PC application. 

Application Samples emUSB-Device CDC






Measurement Device




A target device running emUSB-Device CDC is recognized by the host as a serial interface (USB2COM, virtual COM port), without the need to install a special host driver, because the communication device class is one of the standard device classes and every mayor operating system already provides host drivers for those device classes. All PC software using a COM port will work without modifications with this virtual COM port. Under Windows the device will show up as a COM port, under Linux as a /dev/ACMx device. This allows the user to use host software which was not designed to be used with USB, such as a terminal program.


Components required to use the CDC class:

  • emUSB CDC
  • emUSB-Device core
  • emUSB target driver

Example Application

The start application (in the Application subfolder) is a simple echo server, which can be used to test emUSB-Device. The application receives data byte by byte and sends it back to the host.